<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
 
</head>
<body>
        <div id="app">
            <div class="input-num">
                <button @click="sub"> - </button>
                <span> {{ num }} </span>
                <button @click="add"> + </button>
            </div>
        </div>


</body>
</html>

<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
<script>
       var app = new Vue({

            el:"#app",
            data:{
                num:1
            },
            methods: {
                add:function(){
                    if(this.num<10){
                        this.num++;
                    }

                    else{
                        alert("别点了，最大了");
                    }
                },
                sub:function(){
                    if(this.num>0){
                        this.num--;
                    }
                    else{
                        alert("别点了，最小了");
                    }
                }


                }
            });

</script>